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Growing concern over emissions from increased airport operations has resulted in a need to assess the impact of aviation related activities on local air quality in and around airports, and to develop strategies to mitigate these effects. One such strategy being investigated is the use of alternative fuels in aircraft engines and auxiliary power units (APUs) as a means to diversify fuel supplies and reduce emissions. This paper summarizes the results of a study to characterize the emissions of an APU, a small gas turbine engine, burning conventional Jet A-1, a fully synthetic jet fuel, and other alternative fuels with varying compositions. Gas phase emissions were measured at the engine exit plane while PM emissions were recorded at the exit plane as well as 10 m downstream of the engine. Five percent reduction in NOx emissions and 5-10% reduction in CO emissions were observed for the alternative fuels. Significant reductions in PM emissions at the engine exit plane were achieved with the alternative fuels. However, as the exhaust plume expanded and cooled, organic species were found to condense on the PM. This increase in organic PM elevated the PM mass but had little impact on PM number. [ABSTRACT FROM AUTHOR]

Abstract: The development of kerosene-like drop-in alternative aircraft fuels is currently receiving increased attention. Using a range payload approach the need for drop in fuels is justified. The alternative fuels available can be categorised into two groups; depending on whether the product increases supply security of supply or provides a reduced environmental footprint. This paper uncovers this relationship through a review of commercially available process technologies (Transesterfication, Fischer–Tropsch (FT) and hydroprocessing (HRJ)) to produce alternative fuels. The lifecycle assessments available are reviewed to identify what are actually clean fuels or have the potential to be one. A summary of the recent alternative fuel flight test campaigns is given and there results evaluated along with ground based results. A review of combustion characteristics available for the alternative fuels including ignition characteristics are presented to demonstrate the effect the distillation curve has on combustion and how too narrow a distribution of components in the fuel could generate problems with high altitude relight. The effect alternative fuels have on gaseous emissions regulated by the International Civil Aviation Organisation (ICAO) Committee on Aviation Environmental Protection (CAEP) is discussed and shown to be engine hardware dependant. Experimental data, from an Auxiliary Power Unit (APU) engine, are provided showing how, although the Gas to Liquid (GtL) and Coal to Liquid (CtL) FT fuels may not reduce GHG emissions, even with Carbon Capture and Sequestration (CCS), the local air quality around airports will benefit through reduced particulate emissions. Finally the prospects for future fuel development are discussed. [ABSTRACT FROM AUTHOR]

The work characterizes the changes in volatile and semivolatile PM emissions from a gas turbine engine resulting from burning alternative fuels, specifically gas-to-liquid (GTL), coal-to-liquid (CTL), a blend of Jet A-1 and GTL, biodiesel, and diesel, to the standard Jet A-1. The data presented here, compares the mass spectral fingerprints of the different fuels as measured by the Aerodyne high resolution time-of-flight aerosol mass spectrometer. There were three sample points, two at the exhaust exit plane with dilution added at different locations and another probe located 10 m downstream. For emissions measured at the downstream probe when the engine was operating at high power, all fuels produced chemically similar organic PM, dominated by CxHy fragments, suggesting the presence of long chain alkanes. The second largest contribution came from CxHyOz fragments, possibly from carbonyls or alcohols. For the nondiesel fuels, the highest loadings of organic PM were from the downstream probe at high power. Conversely, the diesel based fuels produced more organic material at low power from one of the exit plane probes. Differences in the composition of the PM for certain fuels were observed as the engine power decreased to idle and the measurements were made closer to the exit plane. [ABSTRACT FROM AUTHOR]